How Ireland protects homeowners with cracking concrete

A house being repaired north of Dublin, Ireland. Pyrite in the crushed-stone fill has caused floor slabs to break in thousands of new homes in the area. Pyrite is similar to pyrrhotite, a mineral that is causing many Connecticut foundations to crack and crumble. (Carolyn Lumsden)

James Lombard winces when recalling his talks with homeowners in Ireland. “You're like doctor telling them they have cancer,” said the engineer with Ground Investigations Ireland.

The bad news is that they have pyrite in their houses. Pyrite is an iron sulfide, like pyrrhotite, which is wrecking homes in eastern Connecticut. Both cause chemical reactions, when exposed to air and water, that make homes crack.

Advertisement

In Irish homes, the pyrite lies in the fill underneath the ground-floor slab. To remediate, crews rip up the floor, excavate the bad stuff and replace it with clean fill. The cost averages $79,000 per home.

In Connecticut, the pyrrhotite lies in concrete foundations. Connecticut’s remediation costs are higher — averaging $168,000 per home — in part because houses must be hoisted for the concrete to be taken out. A new foundation is then poured.

The Irish government is spending $79 million to fix more than 1,600 damaged homes. Connecticut is issuing $100 million in state bonds over five years to fix up to 700 homes. (A $12 yearly tax on home insurance policies is also helping.)

“I’ve just seen so many people affected, and that's wrong,” said Mr. Lombard from his office in the Dublin County countryside. “It should never be allowed to happen again.”

Ireland has put in place many protections for new construction since the pyrite plague came to light there in 2007. Though Ireland’s guidelines have their critics, they exceed any that Connecticut now has.

For one thing, Ireland has clear guidance on the amount of pyrrhotite and pyrite now allowed in construction materials.

Connecticut has to make sure families never have to hear the frightening word “pyrrhotite” from an inspector again.

How To Test Quarries?

Advertisement

There’s debate over how much pyrrhotite in concrete is safe. Zero, of course, but that’s unrealistic.

“You could impose such strict limits to ensure that nothing ever happens, but you might find you've not got any stone that'll actually achieve those limits,” said Paul Forde, chairman of DBFL Consulting Engineers in Dublin.

Also, whether pyrrhotite causes problems can depend on many factors, among them water. “If the water can’t get to the pyrrhotite, the pyrrhotite won’t oxidize,” says Nick Scaglione, an Ohio petrographer who has analyzed a lot of concrete in Connecticut.

But a consensus is emerging that any pyrrhotite over 0.1 percent by mass needs a closer exam. In Canada, a judge ruled in 2014 that pyrrhotite as low at 0.23 percent could damage homes.

It’s helpful to look at Ireland’s new guidelines.

The National Standards Authority of Ireland says quarry aggregate — the crushed stone, sand and other material gong into concrete — should be tested every 60 production days for total sulfur.

Only total sulfur below 0.1 percent is given the green light in Ireland.

If sulfur registers between 1 percent and 0.1 percent, it must undergo a petrographic analysis.

Total sulfur over 1 percent is unacceptable.

Testing “is not enormously expensive” and can avert a disaster, said Mr. Lombard. “In one instance, all the tests were perfect and then all of a sudden, boom, they failed.”

A bill before Connecticut’s legislature would require the state to adopt the even stricter recommendations of the U.S. Army Corps of Engineers.

Connecticut doesn’t exactly do this, though it tried. A recent change in state law requires builders to give town officials the names of “the individual or entity that supplied the concrete” — but not necessarily the name of the quarry. That legislation could be tweaked.

Given Connecticut’s geology and its thirst for new homes, a wee bit more of Ireland’s protections could prevent more heartache here.

Advertisement

Tomorrow: 3 Rules To Stop Another Housing Disaster In Connecticut.

Carolyn Lumsden, the Society of Professional Journalists’ 2018 Pulliam Editorial Writing Fellow, is working in partnership with The Courant to continue to examine Connecticut’s crumbling concrete problem. Lumsden retired in December as The Courant’s opinion editor.